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. 2019 Feb 4;17(2):e3000123. doi: 10.1371/journal.pbio.3000123

Fig 7. Proposed mechanism of RpfR activation by BDSF and RpfF inhibition by RpfR.

Fig 7

At low-cell density (top left), BDSF levels are low and the RpfR PDE domain is minimally active, permitting elevated levels of c-di-GMP and favoring biofilm formation. Here, we depict a theoretical regulatory interaction between the PAS (rainbow cartoon) and PDE (gray box) domains. At high-cell density (top right), BDSF has accumulated and bound to the RpfR PAS domain. This activates the RpfR PDE domain to degrade c-di-GMP to pGpG, favoring biofilm dispersal. Here, we depict RpfR PDE domain dimerization occurring upon BDSF binding; however, PDE activation may also occur via the rearrangement of catalytically inactive (autoinhibited) RpfR dimers. Throughout cellular growth, the RpfR FI domain (purple surface) associates with RpfF (light orange) (bottom), restraining BDSF synthesis, in turn modulating the cellular level of c-di-GMP. BDSF, Burkholderia DSF; c-di-GMP, bis-(3′-5′)-cyclic dimeric guanosine monophosphate; DSF, diffusible signal factor; FI, RpfF interaction; PAS, Per-Arnt-Sim; PDE, phosphodiesterase; pGpG, 5′-phosphoguanylyl-(3′,5′)-guanosine; RpfF, regulation of pathogenicity factor F; RpfR, regulation of pathogenicity factor R.